Cylinder of rotational printing press

ABSTRACT

A cylinder of a rotary printing machine has at least two axially extending cylinder channels on its peripheral surface. These two cylinder channels are offset circumferentially at an angle which is determined depending on the inherent bending frequency vibration f vib  of the cylinder.

FIELD OF THE INVENTION

The present invention is directed to a cylinder of a rotary printingpress. Two channels in the cylinder are offset with respect to eachother in the circumferential direction.

BACKGROUND OF THE INVENTION

DE 198 03 809 A1 and JP 10-071694A disclose transfer cylinders of aprinting press with channels which are arranged offset by 180°.

SUMMARY OF THE INVENTION

The object of the present invention is directed to providing a cylinderfor a rotary printing press.

In accordance with the present invention, this object is attained byproviding the cylinder with at least two channels or grooves which aresituated on the surface of the cylinder and which are offset at an anglein the circumferential direction of the cylinder. The angular offset isdetermined as a function of the inherent bending frequency of thecylinder. This offset is preferably between 5° and 40°.

The advantages which can be achieved by the present invention primarilylie in that the amplitude of the cylinder vibration is minimized bypassive vibration damping.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention is represented in thedrawings and will be described in greater detail in what follows.

Shown are in:

FIG. 1, a cylinder useable for performing printing and having a splitchannel with channel halves which are offset by an angle φ,

FIG. 2, a cylinder useable for performing printing, having threechannels offset by an angle φ,

FIG. 3, a cylinder for performing printing, having four channels offsetby an angle φ,

FIG. 4, an arrangement of channels in cooperating cylinders of equalcircumference for performing printing, and in

FIG. 5, a graph showing vibration amplitudes after overrolling the pairof channels shown in FIG. 1 in comparison to overrolling a singlecontinuous channel, or one extending over half the barrel width. Theamplitudes relate to an “isolated” overrolling, i.e. an amplitudeamplification by previous, not terminated overrolling is not taken intoconsideration.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The amplitude of the resultant total vibration of a cylinder of a rotaryprinting machine, within a definable rate of production range, isminimized, in accordance with the present invention by the destructiveinterference of the vibration excited by sequential channel impacts. Forthis purpose, the destructively interfering channel impacts must followeach other closely in order to best meet the interference conditionswith respect to amplitude and phase relationships, for (a) comparableamplitudes, i.e. the lowest possible vibration damping between theinterfering channel impacts, lead to the greatest possible obliteration,(b) the phase relationship, i.e. the chronological distance between theinterfering channel impacts should vary as little as possible with theproduction rates in order to receive the obliteration over a wide rangeof production rates.

As represented in FIG. 1 to 3, each cylinder performing printing hassplit channels.

The split channels of each cylinder depicted in FIGS. 1 to 3 are offsetfrom each other by a defined angle φ, for example 5° to 40°, or morespecifically 13° to 21°, and most preferably in particular 16° to 18°.

The angle of offset φ for each channel is derived from the inherentbending frequency f_(vib) of the cylinder and the rotation frequencyf_(rot), at which the amplitude should be minimal, and is calculated as

φ=(f _(rot) /f _(vib))*180°

In the course of the structural conversion, a deviation of up to ±20%from the angle φ calculated in this way is permitted.

The channels of adjoining, cooperating printing cylinders of equalcircumference are arranged in such a way that the respective channels onthe adjoining cylinders roll off on each other, as seen in FIG. 4.

The channels of adjoining printing cylinders, wherein a cylinder ofdouble circumference is arranged next to a cylinder of singlecircumference, are arranged in such a way that the channels roll off oneach other during every, or every second, revolution of the cylinder ofsingle circumference.

Efficiency of the Vibration Damping

In the following discussion, the angularly offset channels representedin FIG. 1 and which are offset by the angle φ, as calculated inaccordance with the above equation, and which cylinder with channels isrolling off a similar cylinder, as depicted in FIG. 4, are called a“channel pair”. The resultant vibration amplitude after the channel pairhas been rolled over, compared with the roll-over of a pair of cylinderseach with a single channel extending over the entire barrel width, aswell as in comparison with the roll-over of a pair of cylinders eachwith a single channel extending over half the barrel width, is shown byway of example in FIG. 5 in connection with an angle φ, which isoptimized for the production rate of 70,000 pieces, for examplenewspaper pages, per hour.

The vibration-technological advantages of a cylinder in accordance withthe present invention for performing printing and having a channel pairoffset in accordance with the present invention, over cylindersperforming printing with divided channels, which are offset by adifferent, generally known angle typically of 90° or 180°, and called inwhat follows “conventionally staggered”, are twofold:

Initially, following the roll-over of the channel pair, the vibrationamplitude because of the destructive interference of the channel pair ofthe present invention is lower, by up to 60%, than the vibrationamplitude after the roll-over of a single split channel as shown in thegraph of FIG. 5.

Secondly, following the roll-over of the channel pair of the presentinvention, the excited vibration has available essentially the entirecylinder rotation time 1/f_(rot) for decay while, with conventionallystaggered cylinders, another channel impact occurs within the samecylinder rotation time. This is of importance particularly in connectionwith high production rates, wherein an amplitude amplification, becauseof the superimposition of non-decayed vibrations, takes place.

The cooperation of both of the above discussed effects increases theefficiency of the vibration damping beyond the amount represented inFIG. 5.

Comparison of the Structural Designs in FIGS. 1 to 3

The first harmonic vibration of the bending vibration adds substantiallyto the total vibration amplitude after roll-over of the channel pair.Because the force introduction of the structural design in accordancewith FIG. 2—in contrast to the embodiments in accordance with FIG. 1 andFIG. 3—does not have the symmetry of the first harmonic vibration, thelatter is much less excited in the embodiment in accordance with FIG. 2.Opposed to this is the disadvantage of the embodiment in accordance withFIG. 2 that one channel impact takes place “on the outside”, and theother “on the inside”. This generally causes an excitation of varyingstrength of the base vibration, and therefore a reduction of thevibration damping by destructive interference.

The embodiment of FIG. 1 is believed to be favored over the embodimentsin accordance with FIG. 2 and FIG. 3 in view of the possibilities of itsuse for panoramic printing, as well as the simplicity of introducing themechanical clamping channel elements which it provides.

As a whole, the embodiment in accordance with FIG. 1 thus represents themost favorable embodiment of the present invention.

The cylinder is preferably provided as a forme cylinder or as a transfercylinder with channels for fastening printing plates or rubber blanketsto the peripheral surface of the cylinder.

While a preferred embodiment of a cylinder of a rotational printingpress in accordance with the present invention has been fully andcompletely described hereinabove, it will be apparent to one of skill inthe art that a variety of changes in, for example, the drive for eachcylinder, its support in the rotary printing machine, and the like canbe made without departing from the true spirit and scope of the presentinvention which is accordingly to be limited only by the followingclaims.

What is claimed is:
 1. A cylinder for a rotary printing press, saidcylinder comprising: a cylinder body, said cylinder body having acircumferentially and axially extending cylinder peripheral surface witha cylinder body width: at least first and second split channels eachextending axially in said cylinder peripheral surface over less thansaid cylinder body width, said at least first and second split cylinderchannels being offset with respect to each other at an angle φ in acircumferential direction of said cylinder body, said angle φ of offsetof said split channels with respect to each other being a function of aninherent bending frequency of said cylinder body and wherein said angleφ of offset is between 13° and 21°; and cylinder cover fasteningelements in said at least first and second split channels.
 2. Thecylinder of claim 1 wherein said angle φ is between 16° and 18°.
 3. Thecylinder of claim 1 wherein said cylinder body has a rotation frequencyf_(rot) and further wherein said angle φ is determined also as afunction of said rotation frequency f_(rot).
 4. The cylinder of claim 3wherein said angle φ has the relationship1.2×(f_(rot/)f_(vib))×180°≧angle φ≧0.8×(f_(rot/)f_(vib))×180°.
 5. Thecylinder of claim 3 wherein said angle φ has the relationship angleφ=(f_(rot/)f_(vib))×180°.
 6. The cylinder of claim 3 wherein saidrotation frequency f_(rot) is selected for the minimum vibrationamplitude.
 7. The cylinder of claim 1 wherein said cylinder is a formecylinder.
 8. The cylinder of claim 1 wherein said cylinder is a transfercylinder.